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Author: Seungwon Choi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Animals undergo periods of behavioral quiescence and arousal in response to environmental, circadian, or developmental cues. During larval molts, C. elegans undergoes a period of profound behavioral quiescence termed lethargus. Locomotion quiescence during lethargus was abolished in mutants lacking a neuropeptide receptor (NPR-1), and was reduced in mutants lacking NPR-1 ligands (FLP-18 and -21). Wild type strains are polymorphic for the npr-1 gene, and their lethargus behavior varies correspondingly. Locomotion quiescence and arousal were mediated by decreased and increased secretion of an arousal neuropeptide (PDF-1) from central neurons. PDF receptors (PDFR-1) expressed in peripheral mechanosensory neurons enhanced touch-evoked calcium transients. Thus, a central circuit stimulates arousal from lethargus by enhancing the sensitivity of peripheral mechanosensory neurons in the body. These results define a circuit mechanism controlling a developmentally programmed form of quiescence.
Author: Seungwon Choi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Animals undergo periods of behavioral quiescence and arousal in response to environmental, circadian, or developmental cues. During larval molts, C. elegans undergoes a period of profound behavioral quiescence termed lethargus. Locomotion quiescence during lethargus was abolished in mutants lacking a neuropeptide receptor (NPR-1), and was reduced in mutants lacking NPR-1 ligands (FLP-18 and -21). Wild type strains are polymorphic for the npr-1 gene, and their lethargus behavior varies correspondingly. Locomotion quiescence and arousal were mediated by decreased and increased secretion of an arousal neuropeptide (PDF-1) from central neurons. PDF receptors (PDFR-1) expressed in peripheral mechanosensory neurons enhanced touch-evoked calcium transients. Thus, a central circuit stimulates arousal from lethargus by enhancing the sensitivity of peripheral mechanosensory neurons in the body. These results define a circuit mechanism controlling a developmentally programmed form of quiescence.
Author: Kelsey P. Taylor
Publisher:
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Category :
Languages : en
Pages :
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Animals switch between periods of behavioral quiescence and arousal in response to environmental, circadian, or developmental cues. C. elegans exhibit periods of behavioral quiescence during larval molts (termed lethargus) and as adults. Little is known about the circuit mechanisms that establish these quiescent states. Mutants lacking the neuropeptide receptor NPR-1 are a model for heightened arousal and have dramatically reduced locomotion quiescence during lethargus as a result of increased sensory acuity and secretion of the arousal peptide PDF-1.
Author: Julia Ann Kaye
Publisher:
ISBN:
Category :
Languages : en
Pages : 350
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Author: Zhiyong Shao
Publisher: Frontiers Media SA
ISBN: 2832506399
Category : Science
Languages : en
Pages : 252
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Author: Corinne Lenore Pender
Publisher:
ISBN:
Category :
Languages : en
Pages : 232
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The transcriptional response controlling adaptation to internal and environmental hypoxia is broadly conserved in animals. The key mediator of this response is the transcription factor HIF (hypoxia-inducible factor), which is active only in hypoxia due to the function of its negative regulators, the prolyl hydroxylase EGLN and the E3 ubiquitin ligase complex recognition subunit pVHL. HIF drives transcription of hundreds of targets that promote hypoxia adaptation. Recent work has also described important and broad roles for HIF outside of the traditional hypoxia response, including functions in immunity, oxidative and other stress responses, and behavior; how HIF targets drive these aspects of animal physiology is poorly understood. In this dissertation, I describe genetic analyses of the nematode C. elegans that have provided insight into the function of HIF targets in regulating animal physiology and behavior. The EGLN family was defined by the C. elegans homolog, EGL-9. Prior to the identification of EGL-9 as a HIF hydroxylase, our laboratory discovered the egl-9 gene from studies of egg-laying behavior. egl-9 loss-of-function mutants, in which HIF is constitutively active, are egg-laying defective; the mechanism regulating egg laying downstream of HIF has been unknown. From a screen for suppressors of the egl-9(lf) egg-laying defect, we identified the gene cyp-36A1, which encodes a cytochrome P450 enzyme and is likely a direct transcriptional target of HIF. In addition to modulating egg-laying behavior downstream of HIF, CYP-36A1 controls expression of more than a third of HIF-upregulated genes and regulates multiple stress responses. A screen for suppressors of cyp-36A1(lf) identified the nuclear hormone receptor NHR-46. We propose that CYP-36A1 functions as a hormone biosynthetic enzyme for the ligand of this receptor, thus mediating gene expression changes that alter stress physiology and behavior. We also found site-of-action and genetic evidence for at least one additional pathway acting downstream of EGL-9 and HIF-1 to regulate egg-laying behavior. These studies have identified novel HIF effectors that broadly affect physiology and behavior in C. elegans, and reveal new avenues for future work on regulation of HIF-controlled biology.
Author: John H. Byrne
Publisher: Oxford University Press
ISBN: 0190456787
Category : Science
Languages : en
Pages : 1304
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Invertebrates have proven to be extremely useful model systems for gaining insights into the neural and molecular mechanisms of sensory processing, motor control and higher functions such as feeding behavior, learning and memory, navigation, and social behavior. A major factor in their enormous contributions to neuroscience is the relative simplicity of invertebrate nervous systems. In addition, some invertebrates, primarily the molluscs, have large cells, which allow analyses to take place at the level of individually identified neurons. Individual neurons can be surgically removed and assayed for expression of membrane channels, levels of second messengers, protein phosphorylation, and RNA and protein synthesis. Moreover, peptides and nucleotides can be injected into individual neurons. Other invertebrate model systems such as Drosophila and Caenorhabditis elegans offer tremendous advantages for obtaining insights into the neuronal bases of behavior through the application of genetic approaches. The Oxford Handbook of Invertebrate Neurobiology reviews the many neurobiological principles that have emerged from invertebrate analyses, such as motor pattern generation, mechanisms of synaptic transmission, and learning and memory. It also covers general features of the neurobiology of invertebrate circadian rhythms, development, and regeneration and reproduction. Some neurobiological phenomena are species-specific and diverse, especially in the domain of the neuronal control of locomotion and camouflage. Thus, separate chapters are provided on the control of swimming in annelids, crustaea and molluscs, locomotion in hexapods, and camouflage in cephalopods. Unique features of the handbook include chapters that review social behavior and intentionality in invertebrates. A chapter is devoted to summarizing past contributions of invertebrates to the understanding of nervous systems and identifying areas for future studies that will continue to advance that understanding.
Author: Zoë Alyse Hilbert
Publisher:
ISBN:
Category :
Languages : en
Pages : 140
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Sexual dimorphisms are a fundamental feature of the nervous systems of diverse animal species and the identification and functional characterization of such features is critical to our understanding of differences in behavior between the sexes. While sexual dimorphisms in nervous system organization and morphology can contribute to behavioral differences, increasingly, roles are being defined for more subtle differences in the regulation of sexually dimorphic behaviors. Chapter One of this thesis discusses sexual dimorphisms in the nervous systems and behaviors of several species, with particular focus on work in the nematode, Caenorhabditis elegans. In Chapter Two, we show that sexual dimorphism in a central neuroendocrine signaling pathway in C. elegans is essential for establishing sex differences in decision-making behaviors. We demonstrate that the DAF-7/TGF-[beta] ligand is dimorphically expressed in a pair of sensory neurons, the ASJ neurons, in adult male animals and functions to promote male-specific food-leaving behavior. We show that regulation of this expression pattern and the corresponding behavior is dependent on the sex of the animal as well as additional features of its physiological state and its microbial environment. Our work suggests that hierarchical processing and integration of multiple sensory cues within a pair of sensory neurons terminates in transcriptional activation of this neuroendocrine signal, which can help the animal to make behavioral decisions, including whether to stay in a food source or to explore away from it. Defining the genetic pathways that regulate daf- 7 expression in ASJ may provide clues not only to how sexual differentiation occurs in these neurons to promote sex-specific behaviors, but may also inform our understanding of how multiple sensory stimuli are integrated to allow for behavioral adaptation. In Chapter Three, we identify a role for another neuroendocrine signaling pathway, the PDF- 1 neuropeptide pathway, in the sex-specific regulation of daf- 7 expression. Our results demonstrate that neuroendocrine modulation of sex-shared neurons can have profound effects on sexually dimorphic gene expression and behavior. Finally, in Chapter Four, I discuss future directions for this project which include further genetic analysis of daf-7 regulation and aim to provide insight into a range of neurobiological questions in C. elegans.
Author: Nicholas F. Trojanowski
Publisher:
ISBN:
Category :
Languages : en
Pages : 364
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Rhythmic muscular contractions are essential for many different behaviors, from locomotion to respiration. These behaviors are modulated by changes in the external environment, such as temperature shifts and presence of predators, and by internal states, such as hunger and sleep. The roundworm Caenorhabditis elegans feeds on bacteria through rhythmic contraction and relaxation of its pharynx, a neuromuscular pump innervated by a nearly independent network of just 20 neurons. Feeding rate is modulated by many environmental and physiological factors, but feeding generally persists throughout the life of the worm, ceasing only during sleep. The mechanisms by which the pharyngeal nervous system controls feeding during wake and sleep are poorly understood. I used optogenetics, genetics, and pharmacology to define the cholinergic pharyngeal circuitry that regulates feeding rate during wake, and then used similar approaches to examine how feeding is inhibited during sleep. I identified a four-neuron circuit that regulates feeding rate during wake and found that it is degenerate, meaning that multiple different classes of neurons can stimulate feeding in a similar manner. I also found that feeding quiescence is generated by distinct mechanisms during two behaviorally indistinguishable sleep states: cholinergic motor neurons are inhibited during stress-induced sleep, while the muscle is directly inhibited during developmentally timed sleep. Thus, as in mammals and despite its behavioral homogeneity, sleep in C. elegans is not a physiologically homogenous state. These results provide insight into the function of a highly conserved neural circuit that generates robust rhythmic behavior, and illustrate how this circuit can be altered in different ways to produce the same behavioral output during two distinct sleep states.
Author: Ian A. Hope
Publisher: OUP Oxford
ISBN: 019159198X
Category : Science
Languages : en
Pages : 306
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Caenorhabditis Elegans has been a popular model organism for biological research for over thirty years and has been used to investigate many aspects of animal development, for example apoptosis, the Hox genes, signal transduction pathways, and the development of the nervous system. It has recently taken on new importance with the publication of the entire genome sequence in 1998. The first chapter gives all the basic information on C. elegans required to use it: it's natural history, anatomy, life cycle, development, and evolution. Information on how to obtain, grow, and maintain C. elegans for use as a model system is given in Chapter 4. Chapters 2 and 3 describe the genome project and show how to use genome sequence information by searching the database for homologues using different search methods and then how to analyse the search data. The next chapter gives the essential practical details of transformation and common uses for the technique. Chapter 6 covers reverse genetics and describes strategies for gene inactivation that are known to work in C elegans: epigenetic inactivation and mutational germ line inactivation. Chapter 7 is designed to help the user analyse phenotype by microscopy and includes Normaski, fluorescence, 4-dimensional, and electron microscopy. Techniques for studying the neurobiology of C. elegans are given in chapter 8. Chapter 9 describes the three commonly used approaches for studying gene expression and Chapter 10 deals with the common methods of molecular biology essential for gene characterization. C. elegans is not the ideal organism for biochemical studies, but chapter 11 describes several procedures for producing biochemically useful quantities of pure tissues. The final chapter is about conventional genetics and details the standard procedures for selfing and crossing; mutagenesis and mutant screening; characterization of mutants; gene mapping; temperature-shift experiments and mosaic analysis. Caenorhabditis Elegans: A Practical Approach will therefore provide all the background information necessary for use of C. elegans as a model system.
Author: Dorothy T. Krieger
Publisher:
ISBN:
Category : Medical
Languages : en
Pages : 352
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